Two-component diazotype material



United States Patent 3,498,791 TWO-COMPONENT DIAZOTYPE MATERIAL Herbert Rauhut and Roland Moraw, Wiesbaden-Biebrich, Germany, assignors, by mesne assignments, to Keuifel & Esser Company, Morristown, NJ.

No Drawing. Filed Oct. 27, 1966, Ser. No. 589,819 Claims priority, application Germany, Oct. 27, 1965,

Int. Cl. G03c 1/58 US. Cl. 96-91 -2 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a two-component diazotype material with soft gradation, a so-called softworking copying material.

Owing to the photochemical mechanism of the light decomposition of diazo compounds, diazotype materials show a steep gradation if no special measures are taken to obtain a gentle gradation. Due to the attendant relatively limited exposure latitude, originals with weak contrast are easily over or under-exposed when copied on this material. Continuous tones can, therefore, be copied on normal diazocopying materials only with the application of special originals and correct exposure times. Such material is characterized as being hard-working. This property causes no difliculties when technical drawings and letters on transparent paper are copied, because these generally have a sufficient contrast; on the contrary, hardworking material here is advantageous. However, up to now diazotype materials have not been seriously competitive with continuous tone photography employing coatings containing for example silver halides. Even with the soft-working diazotype materials which have recently become known, continuous tone photography was not possible because they do not produce copies with sufficiently correct tones.

Of greater importance for the diazotype material is the field of microfilm duplicating. It is known that documents and drawings are being increasingly filed on microfilms. The microfilms exist mostly in the form of transparent negatives. Frequently, from these copies are required which as near as possible should equal the quality of the original, and, therefore, should also be transparent negatives with a black background. Diazotype materials with transparent supports have proved to be good copying materials here. In most cases, continuously working devices are used for the reproduction, in which original and transparent diazo film are led together past a light source. If originals with varying contrasts and possibly even a narrow range of contrast appear on the silver film to be copied, then it can easily happen that parts of the diazo film are overor under-exposed, because no adjustment of the exposure time for the original inquestion can be made during the continuous run. Here, a diazo film material with a wide exposure latitude is required.

Various means of softening the gradation of diazotype materials have previously been suggested. For example, compositions containing a mixture of light-sensitive diazo compounds or different absorption has been proposed. Similarly azo coupler compounds of dilferent coupling rates have been combined in a diazotype coating in an attempt to broaden the range of good black images. With either of these methods, however, a totally black shade is obtained, at best, in the full shade areas of the original. The continuous tone images, on the other hand, are mostly of green, blue, or violet tinge.

Another method was adopted with the addition of ultraviolet absorbers in the copy coating. In US. Patent No. 3,069,268, diazotype materials are described whose lightsensitive coating consists of several layers with the ultraviolet absorber being contained either alone or in a mixture with the other components in one of the layers. These materials have a gentle gradation and show, in some cases, even an almost correct tone value reproduction. Because of their complicated structure, the materials are, however, difficult to manufacture and are correspondingly more expensive.

A further promising method is described in German Patent No. 906,406. The patent relates to diazotype materials which, for sensitization, contain heavy metal-free organic substances in the light-sensitive coating which strongly absorb light in a special range adjacent to the absorption range of the diazo compound towards the longer wave range. In Examples 1 and 3 of this patent it is mentioned that the diazotype materials manufactured according to this method show a gentle gradation. However, it was found that their gradation is not yet sufficient for microfilm reproduction. The materials described in this patent are also inclined to turn yellow.

In spite of these various suggestions and the obvious need for soft-working microfilm reproduction materials, so far no material has become known which meets practical requirements.

Thus, it is the object of the present invention to pro vide a diazotype material which better meets the demands made for microfilm reproduction than do the materials known so far. More specifically, the object is to provide a combination of ultra-violet absorber with diazo compound and coupling component to produce a soft-working reproduction material whose full shades and continuous tones are black and show no color tinge.

With regard to the demand for nnobjectionable black shades, it has become common practice to use mixtures of blue and yellow azo dye coupling components in the diazotype coating to achieve these shades. Improved yellow couplers have recently been suggested which comprise phenylamines of the general formula ITIH-Rl alkyl in which R stands for one of the groups -COCH CONH or -CSNH or CNHNH If this yellow component is used in combination with a blue component in the light-sensitive coating, then the covering power of the yellow component in the black shade formed during development with ammonia is in itself sufficient to produce copies of even blackness from originals with dilferent densities.

Now it has been found that it is possible according to the present invention to produce a two-component diazotype material which meets the above-noted requirements. Such material comprises a base, which in the present case and in accordance with an object of the present invention, is transparent, and a light-sensitive coating thereon. The coating contains, besides one or several diazo compounds, a blue-developing coupling component and a yellow-developing coupling component, preferably of the group of phenylamines as described above, an ultra-violet absorber as the gradation flattening additive. The material is characterized specifically in that the coating contains at least one light-sensitive diazo compound of the group of unilaterally diazotized p-phenylene diamine derivatives and at least one ultra-violet absorber of the group of pyrazoline derivatives of the general formula wherein R and R may be the same or different and stand for hydrogen or alkyl radicals with up to 6 carbon atoms.

Among others, the following are suitable as p-phenylene-diamine derivative diazo compounds:

1 diazo 4 dirnethylaminobenzene, l-diazo-4-diethylaminobenzene, 1-diazo-4-morpholinobenzene, 1-diazo-4- morpholino 2,5 diethoxybenzene, and l-diaZo-4-morpholino-2,S-dimethoxybenzene.

The qualities of the ultra-violet absorber do not change with the length of the chain of the alkyl substituent as far as the optical qualities are concerned, and as far as the dissolving characteristics in water or in water/ alcohol mixtures are concerned, they change only very little. The ultra-violet absorbers of the above-mentioned general constitution can, for example, be produced by the addition of primary or secondary amines to vinyl sulfones of the general formula C 52 N I The preparation of these compounds is described, e.g. in Belgian Patent No. 661,139 and in the documents filed with Dutch patent application No. 6,503,106, published on Sept. 14, 1965.

Maximum absorption of the pyrazoline compounds lies at about 3660 AU, whereas the maximum absorption of the unilaterally diazotized p-phenylenediamine derivatives lies at about 3800 AU. Consequently, the areas of absorption overlap to a considerable extent. To obtain the advantages of the present invention, the maximum absorption of the ultra-violet absorber should be at a somewhat shorter wave-length than the maximum absorption of the diazo compound. Optimum flattening of gradation has been found to occur when the absorption maxima lie 50 to 200 AU apart. It should be noted, however, that a certain increase in the light-sensitivity of the diazo compound may be caused by the addition of the ultra-violet absorber. If the dilference in the absorption maxima becomes greater, then the sensitizing effect of the ultra- Violet absorber becomes stronger at the expense of the gradation flattening.

Now it is not only the optical qualities mentioned above which are responsible for the quality of the diazotype material. Other conditions must also be fulfilled, for example, the ultra-violet absorber must be soluble in water or water/alcohol mixtures and must be compatible with the remaining dissolved component, and this compatibilty must also apply to the finished reproduction coating because the storability of the material depends upon it to a large extent. Surprisingly, the combination according to the invention largely fulfills this demand. This is especially essential in regard to the diazo compound and the ultraviolet absorber because these are determined by the optical conditions, so that no great choice exists here. In regard to the coupling components, the choice is somewhat wider.

Because of the required black color tone which is produced in an outstanding way with the phenylamines already mentioned as coupling components, the application of these yellow components is very advantageous. Substituted 2-hydroxy-3-naphthoic acid amides have proved especially suitable as blue components.

Manufacture, storage qualities and processability of the diazotype material according to the invention are equal to those of the known materials. The ultra-violet absorber is dissolved in the coating solution in an amount between about 0.05 and 0.3 prefererably about 0.2 parts by weight of ultra-violet absorber per part by weight of diazo compound.

Cellulose acetate films and hydrophilized synthetic materials, especially polyester'and polycarbonate films coated with cellulose acetate, are preferably used as base materials. However, transparent papers and transparentized papers are also useful. In principle, it is also possible to apply non-transparent base materials, such as paper of the usual kind and metal foils, but the copying materials manufactured in this way are not suitable for microfilm duplicating, which is the main field of application of soft-working diazotype material.

It is further to be noted that the addition of the ultra-violet absorber according to the present invention causes no yellowing of the material even over longer storage periods. Due to the fact that absorption begins at waves of a relatively short wave-length, the ultra-violet absorber is practically colorless in an optically homogeneous coating.

The copying material according to the invention shows a distinctly gentler gradation as compared with diazotype material known up to now. Since the true-tone reproduction of diazotype materials is limited to the extent that they do not show a straight line in the D/log It diagram, the gradation cannot be exactly characterized by the gamma values customarily used in photography. With diazotype materials it is customary to apply, as a measurement for the gradation, the steps which become visible when copying a grey step wedge. Normally, a Kodak step wedge is used in which the optical density of a transparent film changes by 0.15 unit from step to step. If this step wedge is copied on diazotype material of the usual kind, 2 to 4 steps become visible, while the diazotype material according to the present invention produces 5 to 7 steps. The material is therefore completely sufliciently soft-working to produce unobjectionable copies during the reproduction of microfilm negatives at a constant rate of reproduction, even if the density and contrast of the originals used is varying.

The invention is explained more in detail in the following examples:

EXAMPLE 1 Cellulose acetate film is coated with one application of the following solution:

Water ml 38.0 Citric acid g 2.6 Thiourea g 6.0 1- [4' (,B-methylamino-ethyl-sulfonyl) -phenyl] -3-pchlorophenyl-A -pyrazoline g 0.8 2-hydroxy-3-naphthoic acid-B-hydroxy-ethylamide g 1.4 3-hydroxy-4-methyl-phenylurea g 1.75 Formic acid ml 1.2 Isopropanol ml 48.0 1-diazo-4-diethylaminobenzene as fluoborate g 4.0

After drying the coating solution, the cellulose acetate film is exposed under a step wedge and developed with ammonia. Six steps are visible, while with a similar material which contains no ultra-violet absorber only 3 steps are visible. The gradation of the material according to the invention is distinctly gentler than that of the material hitherto used. The color shade of the copy is black in the full shades and, in the continuous tones, the covering power is excellent.

EXAMPLE 2 Cellulose acetate film is coated with one application of the following solution:

Water ml 38.0 Citric acid g 2.5 Thiourea g 6.0 1-[4' ([imethylamino-ethyl-sulfonyl)-phenyl]-3-pchlorophenyl-A -pyrazoline g 1.0 2-hydroxy-3-naphthoic acid-(i-aminoethyl-amide as hydrochloric salt g 1.3 3-hydroxy-4-methylphenylthiourea g 1.9 Formic acid ml 1.2 Isopropanol ml 48.0 1-diazo-4-diethylaminobenzene as fluoborate g 4.0

After drying the coating solution, the cellulose acetate film is exposed under a step wedge and developed with ammonia. In this case, too, copies are obtained with many intermediate steps. If the process is carried out corresponding to the above instructions with the same solution, but without the ultra-violet absorber, then copies with a markedly steeper gradation and poorer covering power are obtained.

The above examples have been presented for the purpose of illustration and should not be taken to limit the scope of the present invention. It will be apparent that the described examples are capable of many variations and modifications which are likewise to be included within the scope of the present invention as set forth in the appended claims.

What is claimed is:

1. Two-component diazotype material consisting essentially of a support and a single layer of a light-sensitive composition thereon comprising:

(a) an azo dye coupler component comprising a mixture of a blue-developing coupler and a yellow-developing coupler selected from the group of phenylamines having the general formula alkyl wherein R represents -COCH CONH CSNH or -CNHNH (b) a p-phenylenediamine-derived light-sensitive diazonium compound; and

(c) a pyrazoline compound having the general formula t nt-Q wherein R and R represent hydrogen or an alkyl radical of up to 6 carbon atoms.

2. Material according to claim 1 wherein said pyrazoline compound is present in an amount of between about 0.05 and 0.3 part per part of light-sensitive diazonium compound.

References Cited UNITED STATES PATENTS 2,432,549 12/1947 Von Glahn et al. 9691 2,639,990 5/1953 Kendall 6t a1. 9682 3,069,268 12/1962 Herrick 96-75 XR 3,113,025 12/1963 Bialczak 96 91 3,248,220 4/1966 Van Rhijn 96 91 3,365,296 1/1968 Cox et al. 96 91 3,378,389 4/1968 Schellhammer et al. 1l733.5

FOREIGN PATENTS 643,042 9/1950 Great Britain.

NORMAN G. TORCHIN, Primary Examiner C. BOWERS, Assistant Examiner U.S. c1. X.R. 

